The invention relates to a torque measuring device for gas turbine engine arrangements, especially gas turbine jet engines (turbo jet engines) for aircraft, where at least one gas turbine jet engine drives one or more supplementary assemblies (generators or the like) with an intermediate reduction or distributor gear.
Gas turbine engines, especially aircraft turbine jet engines, are many times coupled with supplementary power consumers. For example, auxiliary assemblies such as generators for production of current, additional compressors for ventilation of the cabin or for supply of special aircraft lifting devices or the like, are provided.
Depending upon flight conditions, there are quite different loads on the engine which must be detected and responded to in due time in order to avoid overload damage to the engine.
An overload on the engine makes itself known, among other things, by "compressor pumping" which for example can be offset by timely blowdown of compressor air parts, from one or more intermediate compressor stages of the engine. See. U.S. Pat. No. 3,898,799 for background information on such remedial measures.
There is a relatively great difference in engine loads due to driving of auxiliary assemblies for example between normal subsonic flight without afterburning, with unchanged initial setting of the supporting surfaces, and supersonic flight with afterburning and consequently with changed sweepback of the supporting surfaces.
If for example we work from an arrangement of two turbo jet engines per aircraft and conceivable failure of one of the two engines, then the circumstance that the functioning engine must now drive all auxiliary assemblies along will apply almost a double load on the functioning engine, if here we compare the mentioned flight missions in subsonic and supersonic flight.
In the framework of the problem that has been outlined above, the invention is concerned with providing a torque measuring device with which different load moments on the drive for the auxiliary assemblies, arising because of different flight missions and operating conditions, will be detected as rapidly as possible, in a relatively simple way.
In particularly preferred embodiments of the present invention, the torque measuring apparatus includes a first rotatable shaft drivingly engageable with the turbo jet engine, a second rotatable shaft in driving engagement with at least one auxiliary assembly, and a third rotatable shaft interposed between the first and second shafts for transmitting torque therebetween, the third shaft being elastically deformable in response to the magnitude of torque being transmitted so that a resultant relative rotation of the first and second shafts results corresponding to the torque applied. To facilitate detection and measuring of the torque, sensors are provided for detecting the relative rotative positions of said first and second shafts.
In particularly preferred embodiments of the invention the third shaft is continuously connected with each of the respective first and second shafts by interengaging toothed arrangements. According to a still further feature of a particularly preferred embodiment of the invention, a further toothed arrangement is provided for drivingly connecting the first and second shafts directly to one another in bypassing relationship to the third shaft. This last-mentioned toothed arrangement includes teeth at the respective first and second shafts which are circumferentially spaced from one another during normal torque loading operations, the same being interengageable only upon exceeding a predetermined torque limit as controlled by the elastically deformable third shaft. In this manner, the torque can be continuously monitored over the range from zero torque up to the predetermined torque loading where the third shaft is effectively twisted enough so that the direct engagement of the teeth at the first and second shafts results, during which time both the driving connection via the third shaft and the driving connection directly from the first to the second shaft takes place.
According to a still further advantageous feature of a particularly preferred embodiment of the invention, the first shaft is provided with an intentional breaking point, whereby, upon exceeding a predetermined critical excessive torque limit, the first shaft is severed, and the drive train between the engine and the auxiliary assemblies is interrupted. In a particular advantageous embodiment, the portion of the first shaft remaining after such a breakage, is bearingly supported for rotation about the first shaft by means of bearings interposed between the first and second shafts.
The torque measuring apparatus of the present invention offers many advantages. In view of the overlapping telescoping arrangement of the shafts which accommodate the transmittal of torque between the engine and the auxiliaries, a particularly compact construction is provided. Further, since the elastically deformable shaft is continuously drivingly engageable between the first and second shafts, and need not be shifted into and out of engagement, a very economical to manufacture device, with high reliability is obtained. With the construction of the present invention, the parts are easily individually exchangeable. The initial or null setting of the torque measuring device can be accommodated in a very simple manner by the provision of the electro-magnetic sensor devices as being mounted in a turnable holder, a feature which obviates manufacturing tolerance problems that may arise due to the formation of the teeth in the shafts in the drive train of the torque measuring device. With the simple arrangement of the present invention, the measurement range for the torque can be precisely defined, with simple precalibration of the respective third shafts (elastically deformable shafts interconnecting the first and second shafts and allowing relative rotation thereof as a function of the torque applied).
The torque measuring devices of the present invention also exhibit functional capability in both directions of flow of force, as well as over a broad temperature range.
These and further objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show for purposes of illustration only, a single embodiment in accordance with the present invention.